The primary difference between SSD (Solid State Drive) and HDD (Hard Disk Drive) storage devices lies in their technology and performance characteristics. SSDs use NAND flash memory to store data, offering faster read and write speeds, greater durability, and lower power consumption compared to HDDs, which rely on spinning disks and mechanical arms. While SSDs are generally more expensive per gigabyte, their speed advantages significantly enhance boot times and application performance. HDDs, however, provide more storage at lower costs, making them suitable for bulk data storage but slower in access times.